class ActiveSupport::Cache::MemCacheStore

A cache store implementation which stores data in Memcached: memcached.org/

This is currently the most popular cache store for production websites.

Special features:

MemCacheStore implements the Strategy::LocalCache strategy which implements an in-memory cache inside of a block.

Constants

ESCAPE_KEY_CHARS

Public Class Methods

new(*addresses) click to toggle source

Creates a new MemCacheStore object, with the given memcached server addresses. Each address is either a host name, or a host-with-port string in the form of “host_name:port”. For example:

ActiveSupport::Cache::MemCacheStore.new("localhost", "server-downstairs.localnetwork:8229")

If no addresses are specified, then MemCacheStore will connect to localhost port 11211 (the default memcached port).

Calls superclass method ActiveSupport::Cache::Store.new
# File lib/active_support/cache/mem_cache_store.rb, line 76
def initialize(*addresses)
  addresses = addresses.flatten
  options = addresses.extract_options!
  super(options)

  unless [String, Dalli::Client, NilClass].include?(addresses.first.class)
    raise ArgumentError, "First argument must be an empty array, an array of hosts or a Dalli::Client instance."
  end
  if addresses.first.is_a?(Dalli::Client)
    @data = addresses.first
  else
    mem_cache_options = options.dup
    UNIVERSAL_OPTIONS.each{|name| mem_cache_options.delete(name)}
    @data = self.class.build_mem_cache(*(addresses + [mem_cache_options]))
  end
end

Public Instance Methods

clear(options = nil) click to toggle source

Clear the entire cache on all memcached servers. This method should be used with care when shared cache is being used.

# File lib/active_support/cache/mem_cache_store.rb, line 137
def clear(options = nil)
  rescue_error_with(nil) { @data.flush_all }
end
read_multi(*names) click to toggle source

Reads multiple values from the cache using a single call to the servers for all keys. Options can be passed in the last argument.

# File lib/active_support/cache/mem_cache_store.rb, line 95
def read_multi(*names)
  options = names.extract_options!
  options = merged_options(options)

  keys_to_names = Hash[names.map{|name| [normalize_key(name, options), name]}]
  raw_values = @data.get_multi(keys_to_names.keys)
  values = {}
  raw_values.each do |key, value|
    entry = deserialize_entry(value)
    values[keys_to_names[key]] = entry.value unless entry.expired?
  end
  values
end
stats() click to toggle source

Get the statistics from the memcached servers.

# File lib/active_support/cache/mem_cache_store.rb, line 142
def stats
  @data.stats
end

Private Instance Methods

deserialize_entry(raw_value) click to toggle source
# File lib/active_support/cache/mem_cache_store.rb, line 192
def deserialize_entry(raw_value)
  if raw_value
    entry = Marshal.load(raw_value) rescue raw_value
    entry.is_a?(Entry) ? entry : Entry.new(entry)
  end
end
escape_key(key) click to toggle source
# File lib/active_support/cache/mem_cache_store.rb, line 184
        def escape_key(key)
          ActiveSupport::Deprecation.warn("            `escape_key` is deprecated and will be removed from Rails 5.1.
            Please use `normalize_key` which will return a fully resolved key or nothing.
".strip_heredoc)
          key
        end
normalize_key(key, options) click to toggle source

Memcache keys are binaries. So we need to force their encoding to binary before applying the regular expression to ensure we are escaping all characters properly.

# File lib/active_support/cache/mem_cache_store.rb, line 176
def normalize_key(key, options)
  key = super.dup
  key = key.force_encoding(Encoding::ASCII_8BIT)
  key = key.gsub(ESCAPE_KEY_CHARS){ |match| "%#{match.getbyte(0).to_s(16).upcase}" }
  key = "#{key[0, 213]}:md5:#{Digest::MD5.hexdigest(key)}" if key.size > 250
  key
end
rescue_error_with(fallback) { || ... } click to toggle source
# File lib/active_support/cache/mem_cache_store.rb, line 199
def rescue_error_with(fallback)
  yield
rescue Dalli::DalliError => e
  logger.error("DalliError (#{e}): #{e.message}") if logger
  fallback
end